No abstract

Co-contamination of polycyclic aromatic hydrocarbons (PAHs) with heavy metals (HMs) in aquatic environments is a global threat; however, little is understood about PAH biodegradation in these sites. In this study, PAHs' biodegradation in the presence of HMs in water by a metal-tolerant consortium composed of Bacillus subtilis and fungus Acremonium sp. was investigated. The consortium demonstrated higher tolerance to the tested HMs (Fe, Al, Ni, Cu, Mn and Zn) than the individual consortium components, and the tolerance to individual metals decreased with increasing metal concentrations. In the absence of HMs in aquatic systems, the consortium efficiently degraded naphthalene, fluorine, phenanthrene, anthracene and fluoranthene individually (50 mmol/L) over 10 days. However, while Ni supplementation (5 mmol/L) suppressed phenanthrene and anthracene removal (p ≤ 0.01), enhanced fluoranthene degradation relative to the control was observed. Cu, Zn, Fe and Al supplementation demonstrated significant inhibition against individual phenanthrene, anthracene and fluoranthene removal, and Cu showed a more significant effect on the degradation of these PAH compounds compared to other metals. Conversely, Mn significantly enhanced the removal of fluorene, phenanthrene and fluoranthene, but inhibited anthracene degradation. HM contamination in aquatic systems did not show any effect on naphthalene bioremediation, possible due to its rapid degradation over a short time. Thus, metals affect PAH aquatic biodegradation by consortia, depending on metal species and PAH compound, underlining the complex nature of co-contaminated systems containing HMs and PAHs. To our knowledge, this is the first study to examine the influence of HMs on PAHs' bioremediation by such PAH-degrading consortia in water.

The co-occurrence of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) is very common in contaminated environments. It is of paramount importance and great challenge to exploit a bioremediation to remove PAHs in these environments with combined pollution. We approached this question by probing the influence of HMs coexisting with PAHs on the removal of PAHs by Acremonium sp. P0997 possessing metal resistance. A removal capability for naphthalene, fluorene, phenanthrene, anthracene, and fluoranthenepresentalone (98.6, 99.3, 89.9, 60.4, and 70 %, respectively) and in a mixture (96.9, 71.8, 67.0, 85.0, and 87.9 %, respectively) was achieved in mineral culture inoculated with Acremonium sp. P0997, and this strain also displayed high resistance to the individual HMs (Mn(2+), Fe(2+), Zn(2+), Cu(2+), Al(3+), and Pb(2+)). The removal of individual PAHs existing in a mixture was differently affected by the separately tested HMs. Cu(2+)enhanced the partition process of anthracene to dead or alive mycelia and the contribution of the biosorption by this strain but imposed a little negative influence on the contribution of biodegradation to the total removal of anthracene individually in a culture. However, Mn(2+) had an inhibitory effect on the partition process of anthracene to dead or alive mycelia and decreased the contributions of both biosorption and biodegradation to the total anthracene removal. This work showcased the value of fungi in bioremediation for the environments with combined pollution, and the findings have major implications for the bioremediation of organic pollutants in metal-organic mixed contaminated sites.

The mass transfer of phenol and butyl acetate to/from water was studied in two-phase partitioning bioreactors using immiscible organic solvents and solid polymer beads as the partitioning phases in a 5-L stirred tank bioreactor. Virtually instantaneous mass transfer was observed with phenol in water/2-undecanone, and with butyl acetate in water/silicone oil systems. The mass transfer of butyl acetate to silicone oil was rapid irrespective of the viscosity of the partitioning phase. When Hytrel® polymer beads were employed as the partitioning phase, substrate transport to the polymer was found not to be externally mass transfer limited, but rather internally by substrate diffusion into the polymer. In contrast to gaseous, poorly soluble substrates studied in other works, mass transfer of soluble substrates such as phenol and butyl acetate to the polymer was unaffected by impeller speed but rather by polymer mass fraction.